Re: [PATCH 11/17] odb/source: make `for_each_object()` function pluggable

> Introduce a new callback function in `struct odb_source` to make the
> function pluggable.
>
> Signed-off-by: Patrick Steinhardt <ps@pks.im>
> ---
>  odb.c              | 12 +----------
>  odb.h              | 12 -----------
>  odb/source-files.c | 23 +++++++++++++++++++++
>  odb/source.h       | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 83 insertions(+), 23 deletions(-)
>

> @@ -151,6 +163,27 @@ struct odb_source {
>  	int (*read_object_stream)(struct odb_read_stream **out,
>  				  struct odb_source *source,
>  				  const struct object_id *oid);
> +
> +	/*
> +	 * This callback is expected to iterate over all objects stored in this
> +	 * source and invoke the callback function for each of them. It is
> +	 * valid to yield the same object multiple time. A non-zero exit code
> +	 * from the object callback shall abort iteration.
> +	 *
> +	 * The optional `oi` structure shall be populated similar to how an individual
> +	 * call to `odb_source_read_object_info()` would have behaved. If the caller
> +	 * passes a `NULL` pointer then the object itself shall not be read.
> +	 *
> +	 * The callback is expected to return a negative error code in case the
> +	 * iteration has failed to read all objects, 0 otherwise. When the
> +	 * callback function returns a non-zero error code then that error code
> +	 * should be returned.
> +	 */
> +	int (*for_each_object)(struct odb_source *source,
> +			       const struct object_info *request,
> +			       odb_for_each_object_cb cb,
> +			       void *cb_data,
> +			       unsigned flags);
>  };
>
>  /*
> @@ -233,4 +266,30 @@ static inline int odb_source_read_object_stream(struct odb_read_stream **out,
>  	return source->read_object_stream(out, source, oid);
>  }
>
> +/*
> + * Iterate through all objects contained in the given source and invoke the
> + * callback function for each of them. Returning a non-zero code from the
> + * callback function aborts iteration. There is no guarantee that objects
> + * are only iterated over once.
> + *
> + * The optional `oi` structure shall be populated similar to how an individual
> + * call to `odb_source_read_object_info()` would have behaved. If the caller
> + * passes a `NULL` pointer then the object itself shall not be read.
> + *
> + * The flags is a bitfield of `ODB_FOR_EACH_OBJECT_*` flags. Not all flags may
> + * apply to a specific backend, so whether or not they are honored is defined
> + * by the implementation.
> + *
> + * Returns 0 when all objects have been iterated over, a negative error code in
> + * case iteration has failed, or a non-zero value returned from the callback.
> + */
> +static inline int odb_source_for_each_object(struct odb_source *source,
> +					     const struct object_info *request,
> +					     odb_for_each_object_cb cb,
> +					     void *cb_data,
> +					     unsigned flags)
> +{
> +	return source->for_each_object(source, request, cb, cb_data, flags);
> +}
> +
>  #endif
>
> --
> 2.53.0.536.g309c995771.dirty